1. Field of the Invention
The present invention is directed to a system for communicating with entities on a network.
2. Description of the Related Art
Most machines on the Internet use TCP/IP (Transmission Control Protocol/Internet Protocol) to send data to other machines on the Internet. To transmit data from a source to a destination, the Internet Protocol (IP) uses an IP address. An IP address is four bytes long, which consists of a network number and a host number.
There are at least three different classes of networks currently in use: Class A, Class B and Class C. Each class has a different format for the combination of the network number and the host number in the IP addresses. A Class A address includes one byte to specify the network and three bytes to specify the host. The first bit of a Class A address is a 0 to indicate Class A. A Class B address uses two bytes for the network address and two bytes for the host address. The first two bits of the Class B address are 10 to indicate Class B. The Class C address includes three bytes to specify the network and one byte for the host address. The first three bits of the Class C network address are 110 to indicate Class C. The formats described above allow for 126 Class A networks with 16 million hosts each; 16,382 Class B networks with up to 64K hosts each; and 4 million Class C networks with up to 256 hosts each.
When written out, IP addresses are specified as four numbers separated by dots (e.g. 198.68.70.1). Users and software applications rarely refer to hosts or other resources by their numerical IP address. Instead of using numbers, they use ASCII strings called domain names. A domain name is usually in the form of prefix.name_of_organization.top_level_domain. There are two types of top level domains: generic and countries. The generic domains are com (commercial), edu (educational institutions), gov (the U.S. Federal Government), int (international organizations), mil (the U.S. Armed Forces), net (network providers), and org (non-profit organizations). The country domains include one entry for each country. An example of a domain name is saturn.ttc.com. The term “saturn” is the prefix and may refer to a particular host in the network. The phrase “ttc” is the name of the organization and can be used to identify one or more networks to the outside world. The phrase “com” signifies that this address is in the commercial domain. The Internet uses a Domain Name System (DNS) to convert the domain name to an IP address.
The Internet Protocol has been in use for over two decades. It has worked extremely well, as demonstrated by the exponential growth of the Internet. Unfortunately, the Internet is rapidly becoming a victim of its own popularity it is running out of addresses. Over 4 billion addresses exist, but the practice of organizing the address space into classes wastes millions of addresses. In particular, the problem is the Class B network. For most organizations, a Class A network, with 16 million addresses is too big, and a Class C network with 256 addresses is too small. A Class B network appears to be the right solution for most companies. In reality, however, a Class B address is far too large for most organizations. Many Class B networks have fewer than 50 hosts. A Class C network would have done the job, but many organizations that ask for Class B networks thought that one day they would outgrow the 8 bit host field.
One proposed solution to the depleting address problem is Classless Inter Domain Routing (CIDR). The basic idea behind CIDR is to allocate the remaining Class C networks in varied sized blocks. If a site needs 2,000 addresses, it is given a block of contiguous Class C networks, and not a full Class B network address. In addition to using blocks of contiguous Class C networks as units, the allocation rules for Class C addresses are also changed by partitioning the world into four zones. Each zone includes a predefined number of Class C networks. Although CIDR may buy a few more years time, IP addresses will still run out in the foreseeable future.
Another proposed solution is Network Address Translation (NAT). This concept includes predefining a number of Class C network addresses to be local addresses (also called private addresses). The remainder of the addresses are considered global addresses. Global addresses are unique addresses that should only be used by one entity having access to the Internet. That is, no two entities on the Internet should have the same global address. Local addresses are not unique and are typically used for entities not having direct access to the Internet. Local addresses can be used by more than one organization or network. In the past, a local address could not be used to route on the Internet. Local addresses traditionally can only be used within a private network. NAT assumes that all of the machines on a private network will not need to access the Internet at all times. Therefore, there is no need for each machine to have a global address. A company can function with a small number of global addresses assigned to one or more gateway computers. The remainder of the machines on the private network will be assigned local addresses. When a particular machine on the private network using a local address attempts to initiate a communication to a machine outside of the private network (e.g. via the Internet), the gateway machine will intercept the communication, change the source machine's local address to a global address and set up a table for translation between global addresses and local addresses. The table can contain the destination address, port numbers, sequencing information, byte counts and internal flags for each connection associated with a host address. Inbound packets are compared against entries in the table and permitted through the gateway only if an appropriate connection exists to validate their passage. One problem with the NAT approach is that it only works for communication initiated by a host within the private network to a host on the Internet which has a global IP address. The NAT approach specifically will not work if the communication is initiated by a host outside of the private network and is directed to a host with a local address in the private network.
Another solution that has been proposed is a new version of the Internet Protocol called IPv6 (Internet Protocol version 6, also known as IPng). IPv6 is not compatible with the existing Internet Protocol (IPv4). For example, IPv6 has a longer address than IPv4. Additionally, the IPv6 header is different than the IPv4 header. Because IPv6 is not compatible with IPv4, almost all routing equipment on the Internet must be replaced with updated equipment that is compatible with IPv6. Such widespread replacement of legacy equipment is enormously expensive.
Another proposed solution is the Translating Relaying Internet Architecture Integrating Active Directories (TRIAD). TRIAD includes using a shim protocol between the TCP layer and the IP layer which carries a pair of Internet Relay Tokens (IRTs). An IRT is a potentially opaque variable-length field that extends the addressing beyond that provided by IPv4. The IRTs and the IP headers can include sets of local and global addresses that are changed/shifted at different hops during communication. While TRIAD does help alleviate the diminishing address problem, it requires too many changes to applications, the TCP/IP stack and the various routers along a communication path.
As can be seen, the current proposals to solve the diminishing IP addresses problem are inadequate and/or unduly expensive. Therefore, a system is needed that can effectively alleviate the diminishing IP addresses problem without unreasonable costs.